1. Field
The embodiments described below relate generally to the delivery of adaptive radiation therapy to a patient. In some embodiments, the degree and/or nature of such adaptivity are selectable and conform to a predefined framework.
2. Description
According to conventional radiation therapy, a beam of radiation is directed toward a tumor located within a patient. The radiation beam delivers a predetermined dose of therapeutic radiation to the tumor according to a treatment plan. The delivered radiation kills cells of the tumor by causing ionizations within the cells.
FIG. 1 illustrates a conventional patient treatment process that includes radiation therapy. According to some examples of process 1, image data of a patient is acquired, and a target volume and critical internal structures are identified based on the image data. A radiation dose is prescribed for achieving desired results with respect to the target volume while minimizing damage to the critical structures. Next, a treatment plan for delivering the dose is determined.
The treatment plan is then delivered to the patient during several sessions, or “fractions”, spaced over some period of days. Prior to each fraction, the patient is positioned as required by the treatment plan. Such positioning may involve the use of lasers, skin markers, etc. The relationship between skin markers and the target volume (and other critical structures) is tenuous and may change over time.
However, if relevant portions of the patient are not positioned exactly as required by the treatment plan, the goals of maximizing target radiation and minimizing healthy tissue radiation may not be achieved. More specifically, errors in positioning the patient can result in the delivery of low radiation doses to target tissue and high radiation doses to sensitive healthy tissue. The potential for misdelivery increases with increased positioning errors. Oncologists typically compensate for this potential misdelivery by determining treatment plans that specify lower doses or smaller beam shapes (e.g., beams that do not radiate edges of a tumor) than would be specified if misdelivery was not a consideration.
Systems have attempted to address various aspects of the foregoing. For example, an image of the target volume may be acquired before or after a fraction and reviewed to determine whether the treatment plan is providing the desired results. If not, the patient position or other aspects of the treatment plan may be modified. More efficient adaptation of radiation therapy is desired.